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Warrick is a practicing cardiologist and author with a passion for improving care by helping patients understand their heart health through education. Warrick believes educated patients get the best health care. Discover and understand the latest approaches and technology in heart care and how this might apply to you or someone you love.
Hi, I’m Dr. Warrick and I’d like to welcome you to my consulting room. Today I’d like to speak with you about rate control in atrial fibrillation. When we see someone in the acute setting or someone who has had atrial fibrillation for the first time, often that rhythm is fast and rapid and really quite distressing for the patient. So, one of the things we want to do is to try and slow that heart rate down. It’ll make the patient feel better. It’ll make the heart work better and it’s a good starting point. So, we’re very keen to start to address this as soon as possible. There are a number of drugs that we use to control rate and I’d like to touch on each of those to give a little bit of an overview. Probably one of the most commonly-used drugs are a group of drugs called beta-blockers.
Beta blockers are a class of drug that acts through the receptors that are associated with the sympathetic nervous system. And the sympathetic nervous system is the accelerating nervous system within the body. It’s the process that gives us fight and flight. So, it increases heart rate, it increases blood pressure. The beta blockers act to block the receptors that drive that response. And so they actually act on receptors within the heart to slow the heart. Blocking what would be the accelerating features or factors that could act on the heart. The beta blockers can be given either via tablet or in through the vein. They’re flexible and work very well.
One of the things that we do want to be aware of when we give beta blockers is because they dampen down the sympathetic nervous system, they can also lower the blood pressure. So, we want to keep a close eye on blood pressure and occasionally if the blood pressure is low we may not be able to use beta-blockers in the way we want to. One of the other things that we know about beta blockers is that they can occasionally start asthma. So, in certain patients who may have sensitive airways, we would be very cautious about using beta blockers. But an agent such as Metoprolol which is a very commonly-used beta blocker is very often a first line agent in atrial fibrillation used either as a tablet form – We call that Aurelie or – as an in-the-vein injection. We call that intravenously.
Sometimes we’ll use beta-blockers in conjunction with other medications or we’ll use other medications instead of beta-blockers depending on the heart rate response to the first line of therapy. One of the agents I like to use often in conjunction with beta-blockers is digoxin. Digoxin is from Digitalis and digitalis is from the foxglove plant. You might know a little bit more about plants than I do. But this has been around for many years and it’s a tablet that has effects on the heart. Digoxin can actually be given orally as a tablet, but it can also be given in through the vein. The advantage of digoxin is it has an action on the node that is between the top of the heart and the bottom of the heart that regulates the electrical activity. Going from the atria to the ventricle. So, in atrial fibrillation when this chaotic electrical impulses bombarding the atria-ventricular node leading to ventricular excitation then digoxin acts at the node and slows transmission of electrical signals through the node, therefore meaning that the ventricular right can slow down and be better-controlled.
One of the nice things about Digoxin is it doesn’t tend to lower blood pressure and i...